Re: [PATCH v2] generic: disable dmlogwrites tests on XFS

Christoph Hellwig
2020-08-29T06:48:53Z

On Thu, Aug 27, 2020 at 10:53:29AM -0400, Brian Foster wrote:
> Several generic fstests use dm-log-writes to test the filesystem for
> consistency at various crash recovery points. dm-log-writes and the
> associated replay mechanism rely on discard to clear stale blocks
> when moving to various points in time of the fs. If the storage
> doesn't provide discard zeroing or the discard requests exceed the
> hardcoded maximum (128MB) of the fallback solution to physically
> write zeroes, stale blocks are left around in the target fs. This
> causes issues on XFS if recovery observes metadata from a future
> version of an fs that has been replayed to an older point in time.
> This corrupts the filesystem and leads to spurious test failures
> that are nontrivial to diagnose.
>
> Disable the generic dmlogwrites tests on XFS for the time being.
> This is intended to be a temporary change until a solution is found
> that allows these tests to predictably clear stale data while still
> allowing them to run in a reasonable amount of time.

As said in the other discussion I don't think this is correct. The
intent of the tests is to ensure the data can't be read. You just
happen to trigger over that with XFS, but it also means that tests
don't work correctly on other file systems in that configuration.